The promising MultispeQ device for tracing the effect of seed coating with biostimulants on growth promotion, photosynthetic state and water–nutrient stress tolerance in durum wheat

Seed priming through seed coating with natural biostimulants is a promising approach to enhance plant tolerance to biotic and abiotic stresses. As a result of the wide range of investigated biostimulants and their multitarget effect in plants, high-throughput phenotyping is fundamentally important. An efficient, low-cost and rapid approach for tracking the mode of action of biostimulants is needed. In this work, the effect of seed coating with thyme essential oil and the bacterium Paraburkholderia phytofirmans on plant growth promotion, photosynthetic state and water–nutrient stress tolerance was investigated using the MultispeQ device and the biochemical quantification of abscisic acid (ABA) in wheat seedlings grown under controlled conditions. The MultispeQ device was used to estimate multiple non-invasive measures such as the leaf temperature and thickness, chlorophyll and the photosynthetic state (defined using the standard parameters LEF, qL, ECSt, RFd, Phi2, Fv′/Fm′, NPQt, PhiNPQ, PhiNO). Both treatments enhanced the tolerance to stress evidenced by an enhanced shoot and roots dry matter and photoprotective processes. P. phytofirmans tends to induce lateral root development and enhance photosynthesis. In contrast, thyme oil tends to induce root elongation, water storage capacity and reduce the energy-demanding photosynthetic processes. These results correlated with the endogenous ABA content, used as a reference, highlighting the reliability of the MultispeQ device. This study promotes the importance of phenotyping with the MultispeQ device for achieving better understanding without making invasive measurements.